Sulfur vulcanizate of a diene rubber using a carbazinate derivative as accelerator



United States Patent Int. Cl. C08c 11/54 US. Cl. 260-795 10 Claims ABSTRACT OF THE DISCLOSURE gens, (b) phenyl, (c) nitrile, (d) hydroxy, (e)

NR in which each R is selected from the class consisting of hydrogen and straightor branched-chain alkyl groups of 1 to 4 carbon atoms, and (f) straightand branched-chain and cyclic alkyl groups of 1 to 6 carbon atoms.

This application is a division of my application Ser. No. 504,984 filed Oct. 24, 1955, now US. Patent 3,388,- 146.

This invention relates to the process of sulfur vulcanizing natural and synthetic rubbers using carbazinate derivatives as accelerators, and the rubbers thus produced.

The carbazinate derivatives accelerators have the formula in which each R is a straightor branched-chain alkyl group of 1 to 4 carbon atoms, and in which X is selected from the class consisting of (a) phenylthioformyl and (b) benzene ring is substituted by one or more nitro groups in any one or more positions, and in positions not substituted by a nitro group there is no substituent or one or more substituents from the class consisting of (a) halogens, (b) phenyl, (c) nitrile, (cl) hydroxy, (e) NR in which each R is selected from the class consisting of hydrogen and straightor branched-chain alkyl groups of 1 to 4 carbon atoms, and (1) straightand branched-chain and cyclic alkyl groups of 1 to 6 carbon atoms.

The rubber may be natural rubber or a synthetic polymer of a hydrocarbon diene of 4 to carbon atoms which is a homopolymer or a copolymer of such dienes and also a copolymer butadiene with styrene.

Representative accelerators include the following:

4-nitrophenyl 1,l-dimethyldithiocarbazinate 4-nitrophenyl 1,1-diisopropyldithiocarbazinate 4-nitrophenyl 1,1-sec-butyldithiocarbazinate 4-nitro phenyl 1,1-di-sec-butyldithiocarbazinate 4-nitrophenyl 1,l-di-t-butyldithiocarbazinate 2,4-dinitrophenyl 1,1-diethyldithiocarbazinate 4-nitrophenyl 1,1-di-sec-butyldithiocarbazinate 3, S-dinitrobenzyl 1,1-dimethyldithiocarbazinate 2,6-dinitrophenyl 1,1-di-n-propyldithiocarbazinate Z-nitrophenyl 1,l-n-dibutyldithiocarbazinate 2,5-dinitrobenzoyl 1,1-diethyldithiocarbazinate 3,5-dinitrobenzoyl 1,1-diethyldithiocarbazinate 2-nitro-4-chloro-phenyl 1,1-di-n-butyldithiocarbazanite 2,6 dinitro 3-hydroxy-4-bromo-phenyl 1,1 diethyldithiocarbazinate 2-nitro-4-cyanophenyl 1,1-di-t-butyldithiocarbazinate 2-nitro-biphenyl 1,1-dimethyldithiocarbazinate 3-amino-4-nitrophenyl 1,1-diethyldithiocarbazinate 2-methyl-4-nitrophenyl 1,1-di-n-propyldithiocarbazinate 2-nitro-4-cyclohexyl 1,1-di-n-'butyldithiocarbazinate Z-nitrobenzyl 1,1-diethyldithiocarbazinate S- (phenylthioforlmyl) 1,1-dimethyldithiocarbazinate S-(alkylthioformyl where alkyl is 1 to 4 carbon atoms) 1,1-diethyldithiocarbazinate S-(cyclohexylthioformyl) 1,1-di-n propyldithiocarbazinate S- (biphenylthioformyl) 1,1-di-t-butyldithiocarbazinate The dithiocarbazinates are prepared by the reaction of one mole of unsymmetrical dialkyl hydrazine with one mole of carbon disulfide in an aqueous medium containing 1 mole of sodium hydroxide at a temperature usually above ambient temperature (about 20 C.) and not in excess of 45 or 50 C, or thereabout. After the sodium salt of the carbazinate has been thus formed the mono halogen (preferably the monochloro) derivative of the compound which is to react with the carbazinate is added and the resulting product is precipitated out of the reaction mixture as it forms. After the halogen compound is added the reaction temperature is kept between about 25 and 50 C., and preferably between 35 and 40 C. Identification of the products referred to herein was made by elemental analysis as well as by studying infrared and NMR (nuclear magnetic resonance) spectra.

The following examples are illustrative:

EXAMPLE 1 2,4-dinitrophenyl 1,l-dimethyl-dithiocarbazinate Reactants used:

Moles N,N-dimethylhydrazine 0.20 NaOI-I 0.20 CS 0.20 2,4-dinitrochlorobenzene 0.20

A solution of 8.0 grams of NaOH and 12.0 grams of N,N-dimethylhydrazine in 100 ml. of water was made in a three-neck round-bottom flask, To this solution was added 14.0 grams of CS with cooling to 0 C. The solution warmed up to 30 C. and was stirred during heating and for about one hour. The color changed. During one additional hour of stirring, 40 grams of 1-chloro-2,4- dinitrobenzene in 200 ml. of ethyl alcohol Were added. The solution turned a deep red. It was stirred overnight. Yield was 42 grams, percent, which on recrystallization yielded 2,4-dinitrophenyl 1,l-dimethyldithiocarbazinate with a melting point of 196-197 C EXAMPLE 2 4-nitrobenzyl 1,1-dimethylcarbazinate Example 1 was repeated, but using p-nitrobenzyl-chloride. It yielded 98 percent of yellow solid with a melting point of 182186 C. The elemental structure as determined was in agreement with the following:

3 EXAMPLE 3 S- (phenylthioformyl) 1,1-dimethyldithiocarbazinate Reactants used: Moles N,N-dimethylhydrazine 0.2 NaOH 0.20 CS 0.20 Phenylchlorothioformate 0.20

A solution of 12.0 grams of H N,N(CH and 8.0 grams of NaOH in 150ml. of water was placed in a threeneck, round-bottom flask, cooled to 50 C., and then 15.0 grams CS was added. No reaction occurred. The solution was warmed to 35-40 C. to reflux the CS with stirring for 2-3 hours and a homogeneous solution was obtained. This was cooled to 0 C. by a wet ice bath and 34.4 grams of phenylchlorothioformate was added slowly and the solution turned red. The color changed to yellow with a phase separation. Then 200 to 250 ml. tetrahydrofuran was added to the reaction mixture in the fiask, with constant stirring. The reaction mixture was stirred for 2 hours. Upon evaporation of'the tetrahydrofuran the reaction mixture gave a yellowish precipitate which when recrystallized from isopropyl ether yielded a product of the following formula with a melting point of 149-151 C.:

S O I C It is unexpected that these dithiocarbazinates are active in rubber because compounds of the dithiocarbarnate series having the formula The formula of the masterbatch in each test was:

Parts by weight Emulsion-formed butadiene-styrene copolymer (SB-R) 100 HAF black 50 Zinc oxide 3.0 Stearic acid 2.0 Phenyl-beta-naphthylamine 0.6 Oil 8.0

The cures were effected at 300 F., and the results obtained on 20- and 40-minute cures are recorded below:

Test

Cure 1 2 3 Masterbatch 163. 6 163. 6 163. 6 Accelerator 1. 2 1. 2 1. 2 CEPAR parameters.

Time to 90% cure, 340 F.,

min 7. 9 9. 4 l2. 4 Cure Constant K O. 554 0. 364 0. 245 Mooney Scorch at 265 F;

Ts (Vm-l-l) 31 40 23. Ts (Vm+10) 40 40 40 Vm 24. 0 24. 0 22. 5 Physical properties.

300%Modulus, p.s.i 200 NO 125 40' 725 375 350 400% Modulus, p.s.i 20 325 NC 150 40' 1, 225 625 600 Tensile Strength, p.s.i 20 525 NO 225 40 1, 925 1, 125 975 Ultimate Elongation, percent 20' 760 NO 620 40 600 660 480 M' ThgisglEPAR apparatus II by Glaxton et a1, Rubber World, 143,71,

ay N s nds tor N0 Care.

The foregoing results show that these new compounds are good delayed-action accelerators.

By sulfur vulcanization is meant the curing of rubber by reaction with either free sulfur or a vulcanizing agent of the sulfur-donor type. Known agents of the latter type include the various phenol polysul-fides including the alkyl derivatives thereof, the xanthogen polysulfides, the thiuram disulfides and polysulfides, various amine sulfides including dialkylamine polysulfides and reaction products of primary amines with excess sulfur. One or more accelerator activator is often used with any of the accelerators mentioned, and such activators include the various derivatives of guanidine known in the rubber art, amine salts of inorganic and organic acids, various amines themselves, alkaline salts such as sodium acetate and the like, as well as other activators known to the art. Additionally, two or more accelerators or accelerator combinations are sometimes desirable in a single rubber compound. Vulcanization is usually accomplished by heating a vulcanizable rubber composition at a temperature in the range of 240 to 400 F. for a time ranging from several hours to a few seconds.

Any suitable amount of the accelerator will be used, depending upon the rubber and the use to which the rubber is to be put.

What I claim is:

1. The method of vulcanizing a diene rubber of the class consisting of natural rubber, synthetic homopolymers and copolymers consisting of hydrocarbon dienes of 4 or 5 carbon atoms, and copolymers of butadiene and styrene, which comprises vulcanizing the same in the presence of an accelerating amount of a carbazinate derivative of the following formula:

H R2-N-i I( 3SX in which each R is a straightor branchedchain alkyl group of 1 to 4 carbon atoms, and in which X is selected from the class consisting of (a) penylthioformyl and (b) phenyl, benzyl and benzoyl in which the benzene ring is substituted by one or more nitro groups in any one or more positions, and in positions not substituted by a nitro group there is no substituent or one or more substituents from the class consisting of (a) halogens, (b) phenyl, (c) nitrile, (d) hydroxy, (e) NR in which each R is selected from the class consisting of hydrogen and straightor branched-chain alkyl groups of 1 to 4 carbon atoms, and (f) straightand branched-chain and cyclic alkyl groups of 1 to 6 carbon atoms.

2. The method of claim 1 in which the diene rubber is a butadiene copolymer.

3. The method of claim 1 in which the diene rubber is a butadiene-styrene copolymer and the accelerator is a 2,4 dinitrophenyl1,1-dialkyldithiocarbazinate in which each alkyl group contains 1 to 4 carbon atoms.

4. The method of claim 1 in which the diene rubber is a butadiene-styrene copolymer and the accelerator is S (phenylthioformyl) 1,1 dialkyldithiocarbazinate in which each alkyl group contains 1 to 4 carbon atoms.

5. The method of claim 1 in which the diene rubber is a butadiene-styrene copolymer and the accelerator is 4-nitro-benzyl-1,1-dialkyldithiocarbazinate in which each alkyl group contains 1 to 4 carbon atoms.

6. Sulfur vulcanizate of a diene rubber of the class consisting of natural rubber, synthetic homopolymers and copolymers consisting of hydrocarbon dienes of 4 or 5 carbon atoms, and copolymers of butadiene and styrene, in which a carbazinate derivative of the formula given in claim 1 has been used as an accelerator.

7. The sulfur vulcanizate of claim 6 in which the diene rubber is a butadiene-styrene copolymer.

8. The sulfur vulcanizate of claim 6 in which the diene 5 rubber is a butadiene-styrene copolymer and there was used as an accelerator at 2,4-dinitrophenyl-1,l-dialkyldithiocarbazinate in which each alkyl group contains 1 to 4 carbon atoms.

9. The sulfur vulcanizate of claim 6 in which the dienc rubber is a butadiene-styrene copolymer and there was used as an accelerator S-(phenylthioformyl)-1,1-dialkyldithiocarbazinate in which each alkyl group contains 1 to 4 carbon atoms.

10. The sulfur vulcanizate of claim 6 in which the 10 6 References Cited UNITED STATES PATENTS 2,914,547 11/1959 Gaertner 260429.9 3,244,501 4/1966 DAmico 71-100 3,284,482 11/1966 DAmico et a1. 260-455 JOSEPH L. SCHOFER, Primary Examiner C. A. HENDERSON, JR., Assistant Examiner U.S. C1. X.R.

" UNITED STATES PATENT OFFICE CERTIFICATE OF- CORRECTION patent No. 3, +9 .153 Dated F bru ry 17, 1970 Inventor-(s) Adel F. Halasa It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Col. 1, line 39, "1955" should read --1965'-- line 1 "carbazinate derivatives" should read --carbazinate-derivative-- lines 52-53 should read as follows:

--pheny1, benzyl and benzoyl in which the benzene ring is substituted by one or more nitro groups in any one or more positions, and in positions not subline 63, "of to 5 carbon atoms" should read --of or 5' carbon atoms-' line 65', "also a copolymer butadiene with styrene" should read ---also a copolymer of butadiene with styrene-- SlbiiED AND SEALER SEPZZW LEdvm-d ll. Plumber, 1:. mm 1- mm, JR.

0mm Gomissioner or Pawn- 

